Variable pitch propeller



May 9, 1933- l l R. CHILTON 1,907,504

VARIABLE FITCH PROPELLER y Filed March l, 1929 2 Sheets-Sheet 1 z/ f if ff May 9, 1933. R; CHILTON 1,907,504

VARIABLE FITCH. PROPELLER Filed March l, 1929 2 Sheets-Sheet 2 MAX.

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Mm' /7 L? I N y L w.|VL l I l l j l l l. l I l ll I l l l 0 REM. moo woo zooo INVENTOR Patented May 9, 1933 ROLAND CHILTON, l01?' KEYPORT, N'EW JERSEY, SSIGNOR,

TO UPPERCU CORPORATION, A CORPORATION oFFIcE BY MESNE ASSIGNMENTS, OIF DELAWARE VABABLE FITCH PROPELam Application led March 1,

. This invention relates to variable pitch propellers wherein a pitch increasing blade turning movement is derived from the centrifugal force of theblade,v the movement being opposed by a preset control spring means. The present embodiment constitutes an improvement over that of my copending application, Serial No, 340,214, filed February l5, 1929. e

One object of the present invention is to afford a wider range in the pitch, speed, and torque relationship than is afforded by the mechanism shown in the co-pending application.

Asin the aforesaid application, the propeller of -this invention consists essentially of blades mounted for pitch changing rotation in a'hub, and having the blades secured against centrifugal force by means adapted to generate therefrom the' desired pitch increasing movement in .opposition to a cooperating spring'. The connections include thrust lates -secured to the hub andl blades respectlvely, and themselves connected by means inclined to produce the desired turning movement. In the former case these means compromise balls co-operating with inclined portions of the thrust plates and the inclines are there shown as of constant slope, giving 'a constant ratio between the centrifugal forceand the pitch increasing force derived therefrom, to which in turn the required spring pressure .is directly proportional. Substantial movement of the spring occurs during full pitch change and, with the lowest rate of spring practicable, this involves substantial increase in the spring pressures between the high' and low pitch conditions. A stiffer s ring would give still greater pressure di e'rences but is otherwise desirable Vas beingboth shorter and lighter for .a given .maximum pressure. The type of -characteristics obtainable with a reasonable spring weight with the constant ratio mechanism such as shown in 1929. serial No. 348,070. i

the speed and pitch areincreasing, and detracts from. the eective pressure when the speed and pitch are dereasin exhibiting the well known hysterisis loop characteristic of spring operated, mechanisms. This lowerin of the speed zone of pitch change when t rottling downas compared to that under increasing throttle may be of decided advantage in operation and substantial friction dampening for this purpose may be desirable in certain cases as described hereinafter. l

Fig.v 4 shows an alternative diagram of characteristics which may be preferable in certain aircraft applications and which are obtainable with Athe varying ratio blade rotating mechanism of the present invention.

One ofthe objects of such relationships as illustrated, is to permit of any desired adjustment of the pitch when throttleddown for cruising without-departing from the desired economical engine speed as dic-v tated by considerations of 'maximum power plant life.

It will be seen that the engine output atan?7 given speed is proportional to the prope ler pitch so that the apparently sudden chan e from maximum to minimum pitch` may e accomplished by a relatively widechange in throttle setting and power output z in spite of the slight change in engine speed and therefore in the actuating centrifugal force.

vSuch characteristics require a correspondv`ingly slight changel in the effectivespring reaction against the centrifugal force and this (an important object of the present invention) is secured by thrust means wherein the mechanical advantage of the mechanism upon the spring increases rapidly as the pitch increases.

When inclined thrust faces (3o-operating.

' 100% (corresponding to zero propeller etliciency) when the aircraft is stationary, i. e., on the ground. Loss of effective thrust during the slow speeds of take-off when maximum thrust is desirable (and is available with constant propeller efficiency) therefore occurs with propellers having high pitch suited for high eihciency at normal flying speed.

Referring now again to Fig. 4, it will be seen that the desired low pitch condition may be maintained throughout the take-off period, (of reduced englne R. P. M. with wide open throttle), changing to maximum pitch when free Hight speed has been attained and that this high pitch may be thereafter maintained although the engine be throttled back to the desired reduced power and R. P. M. for cruising economy, and that the actual pitch in use maybe determined by appropriate throttle adjustment without departing from the desired cruising R. P. M. These are objects of the variable pitch propeller of the present invention which may alternatively be regarded as a governor, automatically increasing the load on the power plant as the throttle is opened without departing from the desired economical cruis.

ingengine speed.

y proportioning the rate of increase. in the turning moment from the thrust responsive means to be greater than the rate of increase in spring pressure the device of this invention may be made to give full pitch change without any increase in engine speed,

but of course a substantial increase in throttle opening would be required to generate the necessary increased power to maintain` the speed.

As a further illustration of the utility of this invention the full power dive manoeuvre demanded of modern military aircraft may be cited. This involves extremely high plane speeds and, with fixed pitch propellers, endangers'damage due to overspeeding the power plant. This overspeed may be avoided by the use of a propeller, according to the provisions of this invention, which may be so preset that the pitch will automatically increase to conrensate for the greatly increased speed of'dlve without substantially increasing the power plant R. P. M.

In the drawings:

Figure 1 is a side elevation of the present invention shown partly in section.

Figure 2 is a side elevation disposed at 90 degrees to that of Fig. 1.

Figure 3 is a diagram of characteristics obtainable with a reasonable spring weight with a constant ratio mechanism.

,Figure 4 is an alternative diagram tothat of Fig. 3. Y v

Figure 5 is a sectional detail view on an enlarged scale of the notched connection shown in Fig. 1. i

Referring particularly to Fig. 1, 10 designates the conventional propeller shaft-end of the power plant which is splined at 11 to drivably mount the hub 12 by means of the conventional coned lock ring 13 and the nut 14, which in this case has a long extension 15 for convenience in tightening up. The hub comprises two integral cylindrical extensions 16 towards the outerl ends of which are rigidly secured the thrust rings 17 the propeller blade 21, as by means of interlocking elements 26 andthe clamp connection afforded by the screws 27 and plates 28, are the tubular members 29 provided at their inner ends with lever extensions 30 and bearing on the outside of the cylindrical extensions 16 by means of the bushings 31.

Secured to the hub 12, as by the flange 32, packing ring 33 and bolts 34, is the extended sleeve 35 havinv at its outer end the spring adjusting nut 37. Arranged to slide on the sleeve 35 .and upon. this nut 37 is the outer spring sleeve 38 having an inturned end 39 between which end and the nut 37, the spring 40 is compressed. Ball ended struts 41 coning even t ough the propeller be at rest. To

include the struts 25 in this action it is deV sirable that the elements 43 have inclined contact faces (as shown in F ig. 5)' which are adapted to generate an outward thrust on the propeller blades and thus take up any initial looseness in the parts.

The operation of the device is' as follows: In the low pitch position shown, 'the struts 25 have a minimum, but positive, inclination and as these strutsare sub'ect to the entire centrifugal thrust 'of the blades, they will due to this inclination, generate a turning tendency on the blades and hence on the members 29 and levers 30. This 1s transmitted by the struts 41 tothe sleeves 35 and the spring 40, and, when the speed of rotation generates a suiicient thrust, the spring will be overcome, the sleeve 38 will move to the right and the blades will rotate towards an increased pitch. During this action 1t will be seen that the inclination of the struts 25 increases, increasing the mechanical advantage of the centrifugal force reaction upon the spring and permitting a relatively large increase in pitch in spite of a s ubstantiall accompanying increase inspring pressure without necessarily increasing the centrifugal force or rotational speed. 'Ihe ratios o these quantities can be adjusted by suitably proportioning the initial to the final inclination of the struts, and accordingly a relatively stii and small spring will'be'adequate'to give the desired characteristics as previously described.

For the method of assembly of the blades into the sleeves reference is had to Fig. 2, wherein it will be seen that the outerends of the members 29 are provided with openings 50, normally spaced intermediate of corresponding openings 51 in the plate 28. Onl removal of the bolts 27 the parts may be rotated to bring these openings into register whereby the inturned ends 52 of thev lock` ring 18 are accessible and the ring may be contracted by a suitable tool and withdrawn from its groove in the cylindrical extension 16, all the parts associated with a blade 21 being thus withdrawable as an assembled unit. 'Ihese parts include the tubular member 29, the plate 28, bearing 20, thrust ring 17 and 22, the struts 25,;.and the nut 23, all of which may accordingly be assembled and adjusted before the introduction of the blade mechanism, as a whole, into the hub 12 where it is secured by the lock ring 18 as described, whereafter-the entire mechanism is sealedl against leakage of lubricant ptightening up the bolts 27 with the openinthe end of the member 29 and in the plate 28fcov`ered by the intermediate areas of these members.

It will be noted that in operation there I will' be a high centrifugal tendency on the lubricant contained in the blade operating mechanism member 29 will thus maintain the Vstruts 25 in an initially established submerged condition.

claim: y

1. In a propeller mounting, the combina- Having thus described my invention, Il

and that the inwardly projecting tion of a hub having blademountings, a propeller blade rotationally supported in each mounting, a plurality of elongated elements circumferentially disposed around the blade one end of each of said ti'culated tothe blade and the other end to said mounting and responsive to end pressure so as to cause a limited rotation ofl said blade.

2. In apparatus of the class described, the combination with a mounting member and a member mounted therein for oscillation about an axis of thrust, of a vplurality ofr struts in inclined circumferential disposition about said axis and articulated at respective ends to said members, said struts being responsive to thrust to effect a uni-directional movement of said oscillation, and a yieldable means adapted to effect a return movement when the thrust is relaxed.

3. In apparatus of the class described, the combination with a pair oi members adapted for relative axial and rotary movement, of connecting means Itherebetween adapted to define said movements said connecting means comprising struts articulated to the respective members and spaced around the axis in inclined relation thereto, and a spring means adapted to oppose said movement.

4. In a ing movement, the combination with a first member and a second member the first member adapted for aXial and rotary movement relative tothe second member, of a plurality of circumferentially disposed elements each having an articulate connection with each of said members, said elements being responsive to axial movement of the irst member to change their slope during said movements in a manner as to vary the pitch of the propeller, and a yielding means tending to oppose said change in pitch.

.5. In apparatus of the class described, tlie combination of a hub having a plurality of lblade supporting extensions, a propeller elements being arpropeller adapted for pitch changing force sufiicient to overcome said spring means at a predetermined speed of the hub.

6. In apparatus of the class described, the combination of a hub having a plurality of blade mountings, a propeller blade mounted in each mounting for pitch changing rotation relatively thereto, a preset spring meansopposing said rotation, and a plurality of struts articulated at respective ends to the propeller and to said mountings respectively; said struts having a circumferentially skewed disposition such that an axial thrust of the blade upon said struts will impressa rotational tendency upon the blade in opposition to the action of said spring means.

7. Ina propeller mounting, the combination of a hub having blade mountings, a propeller blade in each mounting adapted for pitch changing rotation relatively thereto, a spring means opposing said rotation,

and a plurality of elongated compression elements each having an end articulated to the propeller blade and to saidA mounting respectively and so disposed that an axial thrust of the blade will cause a circumferential displacement of one end of said `elements relative to the other in such amanner as to overcome said spring means and tov initiate a limited rotation of the blade at a predetermined speed of thehub.- t

'8. In a propeller mounting, the combination. of 'a hub having radially extended mountings rigid therewith, tubular members concentric therewith and supported for relative rotation thereon, a propeller blade mounted `with each tubular member for movement therewith, a spring means tending to maintain the blades at a low pitch position, and thrust transmitting means comprising elements disposed angularly to and circumferentially of said blades and responsive to a predetermined rotational speed of the hub to overcome the spring means and to urge the blades towards a high pitch position.

9. In a propellor y tion of a hub, a radially disposed blade mounting means rigid therewith, a blade rotatably supported in said mounting means, a plurality of circumferentially skewed strut means responsive to the centriugal action of .the blade to actuate the same towards a high .pitch position, and a preset, control means rotating unitarily with said hub and adapted `to maintain the blade -in a low pitch position until a predetermined rotational speed 4ofthe hub is exceeded.

10. In apparatus of the class described, the combination of a first member subject to axial thrust, a second member, -means for deriving a rotation of the irst memberv relative to the second member from said thrust;

said means comprising a plurality of thrust struts 1n helical disposition between said mounting, the combina-` 'members and articulated at their ends to said members. l

11. In apparatus of the class described,

-the combination with a driving member and a driven member organized for relative axial and rotational movement, of 4a conspective members,and a spring means tending to resist said rotational movement.

12. In a'. propeller, in combination, a hub having propel er blade bearings, a blade mounted for slight axial and rotary movement therein, and means for relating said movements comprising helically inclined thrust struts articulated at respective ends to the hub and blade and 'adapted for circumferential change inclination during said movements, and means adapted to yieldingly oppose said movement.

13. In a pitch changing propeller mounting,the combination with propeller blades rotatable about their axes in t e mounting and adapted to maintain a low pitch position at low rotational speed, of a means responsive to the axial thrust of said blades to cause a pitch changing movement of the blades to a high pitch position said means comprising 'a plurality of circumferentially inclined struts articulated respectively at opposed Vends to said blades and to said mounting.

14. In a propeller mounting, the combination of a hub having radially extended mountings rigid therewith, tubular members concentric therewith and supported for relative rotation thereon, a propeller blade mounted in said extension in fixed relation with said tubular members, spring pressure means tending to maintain the blades in one ferentially skewed so as to be responsive to ypitch position and actuating means com-A 'prising a plurality of strut elements circumthe centrifugal thrust of the.blades to cause a pitch changing movement thereof in opposition to said sprin pressure.

Signed at Keyport, 1n the county of Monmouth, and State of'NeW Jersey this 26th day of February, 1929.

ROLAND CHILTON. 

